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I tried asking this question in several forums but didn't find any answers as i expected. It's very hard to find information about halbach array in google, especially in the electromagnetic field.

We know that Halbach array works well with a permanent magnet by giving a strong magnetic field in one side and weak on the other side.

I'm thinking to design solenoid in halbach arrangement to give a strong magnetic field in one side and weak in the other. We know that solenoid behave similarly to permanent magnet. My question what happens when we give alternative current or pulsed dc to solenoid coil? Will the direction change in magnetic field? I know pulsed dc doesn't change in magnetic field? Will this be a problem to achieve halbach array? kindly advise.

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  • \$\begingroup\$ YOU'D HAVE TO GIVE SOME IDEA OF THE WAVEFORMS OF THE VARIOUS COILD TO GET A GOOD IDEA - AND WHAT YOU WERE TRYING TO ACHIEVE. \$\endgroup\$
    – Russell McMahon
    Oct 30 '19 at 5:40
  • \$\begingroup\$ Your stated subject is far less complex than your body text. DC electro magnets with well defined fields - probbly no problem. |Add AC and the fun begins: Applying identical wave sinusoidal signals to solenoids in a Halbach array seems likely to preserve the effects - which are only a result of arithmetic addition. Affects on amplitude of field due to adjacent magnetic materials may well be an issue. | Pulsed DC would be more problematic as the behaviour of field rise and decay would probably be complicated by overall arrangement. \$\endgroup\$
    – Russell McMahon
    Oct 30 '19 at 5:44
  • \$\begingroup\$ I'm trying to create a wireless transmitter using halbach arrangement to produce a magnetic field. I was thinking if we can find a good solution with Halbach arrangement, it will give a high-density magnetic field on one side which will be beneficial for wireless power transmission technologies. This can also increase efficiency but i don't have any idea beside solenoid design. The major drawback with halbach in electromagnetic field is the eddy current and positioning. I was hoping pulsed dc would be an ideal way to get the result. I appreciate your answer. \$\endgroup\$ Oct 30 '19 at 6:04
  • \$\begingroup\$ OK - you reasons for wanting it make sense. Fortunately, with near field coupling, which you have in almost all such applications, you do not get radiation without a load, and at receiver resonance you get excellent power transfer. [[25+ years ago I built a demonstration inductive power transfer system with a 100m loop running around my house and the ability to drop receivers appropriately anywhere along the way. I also had highish speed bidirectionl data signalling across the loop - another story]. Receiver resonance is essentially essential. \$\endgroup\$
    – Russell McMahon
    Oct 30 '19 at 9:28
  • \$\begingroup\$ Thank you for answering. You did a great job with the 100m loop where you can charge a device at anywhere. I'm thinking to use receiver resonance and transmitter resonance but with halbach arrangement for the transmitter since it give us good magnetic field density. What's your suggestion? My idea is to use Halbach AC arrangement for the transmitter. Any suggestion or idea would be useful for my research purpose. \$\endgroup\$ Oct 30 '19 at 9:38
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Halbach array is an alternative to backiron. Backiron closes the loop leaving tiny field on the back side. Halbach closes the loop by force. Is backiron a problem for you? Halbach is more complicated than backiron, i.e. more expensive. In the permanent magnet case it may be created by magnetisation field shape in a single part hence it can be a useful method (refrigerator magnet). With discrete permanent magnets it is a choice between backiron and twice as many magnets. With electromagnets you are talking about twice as much copper. Take your pick. One way or the other the advantage is likely to be small.

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  • \$\begingroup\$ "backiron" returns a rather low amount of results.. Can you elaborate on the subject a bit more or provide a link with details please? \$\endgroup\$ Aug 19 '20 at 17:46
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" "backiron" returns a rather low amount of results" Well, fancy that! The topic of interest is Magnetic Circuits. Analogous to electric current flowing around loops. Magnetic fields form loops. Iron, and multiple other materials, presents a "low impedance" to magnetic field. A block of iron behind an electromagnet closes the loops of the field of the electromagnet such that very little of the field extends beyond the iron. The intermediate magnets of a halbach array confine the field less effectively than iron does. But in certain cases the array may be preferable. e.g. possibly cheaper, possibly simpler, possibly less massive.

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